The present invention relates to data storage systems, and more particularly, this invention relates to a method, system and computer program product for writing data to a tape media.
In magnetic storage systems, data is read from and written onto magnetic recording media utilizing magnetic transducers. Data is written on the magnetic recording media by moving a magnetic recording transducer to a position over the media where the data is to be stored. The magnetic recording transducer then generates a magnetic field, which encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read transducer and then sensing the magnetic field of the magnetic media. Read and write operations may be independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media.
There are occasions where one wants to store moving pictures taken with a plurality of data sources, for example surveillance cameras, to a single tape medium inserted in a single tape drive. In such a case, a data transfer rate of about one twentieth the maximum transfer rate of the tape medium is generally sufficient in writing data to the tape medium per camera. However, it is often desired to read data from the tape medium as fast as possible.
When pieces of data captured with N cameras are concurrently written to a tape medium, the transfer rate during a read operation is 1/N the maximum transfer rate of the tape medium. This transfer rate results because a moving picture file on the tape medium is fragmented as illustrated in FIG. 1, and when moving picture 1, for example, is read, moving picture fragments (2-X) to (4-X) need to be skipped in order to read all of moving picture fragments (1-X).
One conventional solution is to re-write moving picture data written on a tape medium to the same tape medium or to a different tape medium so that each file is recorded in contiguous locations as illustrated in FIG. 2. This may increase the transfer rate at which a portion of moving picture data is read from the tape medium on demand to the maximum transfer rate of the tape medium. To accomplish this, however, another tape drive and another tape medium for re-writing the data are required. If data is re-written to the same tape medium, the available space on the tape medium decreases by half. Accordingly, recording the same amount of picture data needs a tape medium that has a storage capacity twice as large as required when data is not re-written. Moreover, re-writing data requires extra time and steps.
In another approach, data may be temporarily stored in a buffer and, once data from all cameras has been stored, the data may be written file by file. However, to do so requires a considerably large buffer area and is often not realistic in terms of cost-effectiveness.